The iron blast furnace typically is constructed of a metal shell with a refractory brick lining. The life of the refractory brick lining determines the length of time that the furnace can be kept in operation before the furnace must be shut down for installation of new refractory. Longer refractory life decreases refractory cost and increases the productivity achieved from the furnace. More expensive refractory brick have been used to extend the length of a furnace "campaign". Grouting or gunning of refractory material between the refractory brick and the metal shell has also been used as a repair measure to close the gaps which sometimes form between the shell and the brick. Gaps between the brick and shell decrease heat transfer and cause increased wear of the refractory brick.
U.S. Pat. No. 4,510793 discloses the use of a ceramic bar in a furnace wall which wears with the lining. The wear of the bar and the lining is detected ultrasonically by generating ultrasonic pulses in the bar and detecting the reflection of the pulses from the worn inner end of the bar.
Japanese Published Application 1-290709 discloses thermocouples embedded in the refractory on the bottom and bottom side wall part of a blast furnace. From the temperatures measured by the thermocouples, calculations are made to determine the state of packing of coke in the core of the furnace. When the packing of coke is inadequate for preferential flow of molten iron in the central part of the furnace, changes are made in the amount, grain size or hot characteristics of the coke charged to the furnace.
U.S. Pat. No. 4,358,953, Horiuchi et al, discloses a method of monitoring the wear of refractory lining blast furnace walls by sensing temperatures at different points across the thickness of the refractory and analyzing the time delay between trigger signals representing internal phenomena of the furnace and the temperature probe output signals. This patent also describes a prior art method of determining the degree of wear from one dimensional heat transfer analysis. An apparatus for sensing temperature distribution in the refractory is also disclosed. A similar apparatus is disclosed in U.S. Pat. No. 4,412,090, Kawate et al, and in U.S. Pat. No. 4,442,706, Kawate, et al.
It is also known to use one-dimensional and two-dimensional heat transfer calculations to refractory temperature distributions and then later compare with measured temperatures to estimate remaining refractory and skull thickness. A method of this type is disclosed in a literature paper entitled "Evaluation of Mathematical Model for Estimating Refractory Wear and Solidified Layer in the Blast Furnace Hearth", by Suh Young-Keun et al, ISIJ, 1994, Pages 223-228. However, no method previously existed for using measured temperatures to calculate the thickness of the brick and skull directly in a manner which considers interaction between measured temperatures at all locations in a vertical plane simultaneously. Also, no previous method existed that could be used on-line without human intervention to signal problems with gap formation, inefficient cooling on the shell, and to discern the irregular "elephant-shaped" erosion profiles and "bowl-shaped" erosion profiles, so as to enable corrective measures to be taken during furnace operation in order to extend the life of the refractory.
Other patents related to the measurement of wall thickness and/or temperature include U.S. Pat. Nos. 2,264,968; 2,987,685; 2,994,219;3,018,663; 3,307,401; 3,512,413; 4,217,544; 4,248,809; and 4,539,846.